This invention relates to devices that respond to fluid pressure, and is more specifically concerned with an elongated flexible probe having hydraulic or pneumatic focusing in its imager or camera section.
A borescope, endoscope, or similar flexible probe can be generally configured as an elongated flexible insertion tube with a viewing head at its distal or forward end and a control housing for controlling or steering the distal or forward end. The typical borescope has a bendable tubular steering section or articulation section at the distal end adjacent the viewing head. The viewing head, which can be optical i.e. (fiber optic) or video (e.g., a CCD imager), can be situated in the distal fitting of the bending neck. A signal conduit or bundle, which can be a wire bundle in the case of a video device or a fiber optic bundle in the case of an optical device, passes from the head through the insertion tube exiting to a suitable viewing device. A fiber optic bundle is also used to carry illumination to the viewing head for illuminating a target in an enclosed area.
The camera in a video borescope or endoscope typically has a fixed-focus lens assembly with a small aperture so as to have a large depth of field. Because of the small lens aperture, the required illumination has to be rather strong, and especially so when a color image is to be presented.
While focusing systems are theoretically possible, no one has previously proposed a highly reliable yet simple system which could be incorporated into a small-diameter probe.
A bellows-type arrangement for moving the objective lens of an optical type borescope or endoscope is shown in U.S. Pat. No. 4,620,769. Pressure is supplied through a small tube to a bellows unit to move a lens. The bellows expands or contracts in accordance with the applied pressure. Oil is used as a working fluid.
U.S. Pat. No. 4,794,912 describes a braid-and-bladder pneumatic or hydraulic "muscle," i.e., linear traction motor. The purpose of that motor is to articulate or bend a portion of the probe just proximal to the viewing head.